Pump



BAGSJ 14 Oct. 29; 1968 E. H. BLAcKwELL PUMP 2 Sheets-Sheet l Filed 001'.. 19, 1966 y ii P M i m i .L P M w T M R m m m m m m M DI G l0 2O 30 40 50 60 70 8O 90 |00 HO |20 130 l40 DISCHARGE PRESS PSI u m C m 5 H. l T, m n.. E

INVENTOR Oct. 29, 1968 E. H. BLACKWELL.

PUMP

2 Sheets-Sheet 2 Filed Oct. 19, 1966 United States Patent O 3,408,114 p PUMP Elliott H. Blackwell, Warren, Mass., assigner t Warren Pumps, Inc., Warren, Mass., a corporation of Massachusetts Filed Oct. 19, 1966, Ser. No. 587,755 3 Claims. (Cl. 302-14) ABSTRACT F THE DISCLGSURE This invention relates to a pump and, more particularly, to apparatus .arranged to bring about the iiow of materials in a conduit system by means of relatively moving conjugate 'surfaces wherein means is provided for tapping gas from the system at a point where gas is formed.

When a heterogeneous mixture of solids, fluids, and

gases is pressurized in a rotary pump, there is frequently a tendency for some elements of the mixture to separate, according to their relative density and viscosity, due to the mechanical action of the pumping rotor. Occasionally, such a separation facilitates a localized slip of the light or less-viscous iluid. This slip reduces the volumetric efficiency of the pump and may, with sufficient mechanical clearances in the pump, become great enough to displace a portion of the normal intake. If the light or lessviscous fluid, such as air or water, is not a necessary part of the mixture to be pumped, it may be desirable to remove a suflicient portion of it as it is pressurized and before there is much slip. In other words, the slip of one o f the fluids in a localized area in the pump causes the pump to operate less efficiently, requiring a more expensive, larger size pump for a given amount of pumping capacity. In addition, the presence of this material in the original mixture may be undesirable for other reasons and it may be advantageous to yremove it. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide a pump which is eicient in operation even when used with mixtures of separable components.

Another object of this invention is the provision of a pump having means for separating a component of a mixture and carrying it to an area of disposal.

A further object of the present invention is the provision of a pump which is particularly useful for pumping l wood pulp with water and air mixtures and for doing so with considerable eiciency by the removal of the air.

It is another object of the instant invention to provide a pump in which the volumetric eiciency is of a high value when handling partially separated heterogeneous mixtures of solids, liquids and gases because the high- 'slip liquid is removed from the pressurizing area.

It is a further object of the invention to provide a pump in which undesirable excess light iluid can be removed from a system handling a heterogeneous mixture through a rotary pump; for instance, air may be removed from a paper stock and water mixture; light liquids may be removed from some slurries and emulsions.

A still further object of this invention is the provision of a pump system capable of permitting the removal of a separated effluent, which removal can be closely controlled and directed to a suitable portion of the system.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts 'set forth in the specification and covered by the claims appended hereto.

The character of the invention, however, may be best nr Y ICC

understood by reference to one of its structural forms as illustrated by the accompanying drawings in which:

FIG. 1 is a perspective view of a pump embodying the principles of the present invention,

FIG. 2 is a transverse sectional view of the invention taken on the line II-II of FIG. 1,

FIG. 3 is a vertical longitudinal sectional view of a porticn of the pump taken on the line III-III of FIG.

FIG. 4 is a graph showing improvement in the volu metric eiciency of the pump by use of the present invention.

Referring rst to FIG. l, wherein are best shown the general features of the invention, the pump, indicated generally by the reference numeral 10, is shown as mounted on a base 11 and 'shown as being driven through a gear reduction unit 12. The pump is provided with a housing 13 having an inlet opening 14 and an outlet opening 15. The pump is of the double screw type shown and described in the patent of Zalis No. 3,198,582 which issued Aug. 3, 1965, and also shown in the patent of Zalis No. 3,198,132 which issued Aug. 3, 1965. Within the housing are mounted twin 'screws which extendv from the inlet opening 14 to the outlet opening 15, as will be described more fully hereinafter.

Referring to FIG. 3, it can be seen that one of the screws 16 is formed with a conjugate surface 17 and an outercylindrical peripheral surface 18. The outboard end of the rotor or screw 16 is suitably supported in a bearing housing 19 which is provided with a bearing 21 .and a seal 22. Entering the housing 13 between the inlet opening 14 and the outlet opening 15 is an opening 23 in the form of a small bore to which is threadedly fastened a conduit 24 leading to a valve 25. From the valve extends another conduit 26 connected to an opening 27 possing through the wall of the housing 13 into the inlet opening 14.

As is evident in FIG. 2, the other screw 28 is provided with a conjugate surface 29 which mates with the conjugate surface 17 of the 'screw 16 in the usual way. It is also provided with va peripheral surface 31. Adjacent this peripheral surface 313 the housing 13 is provided with an opening 32 to which is connected a conduit 33 leading to a valve 34 from which extends a conduit 35 leading to the wall of the inlet opening 14. It can be seen in FIG. 2 that the screws 16 and 28 rotate in counter-rotation and that the openings 23 and 32 are located closely adjacent to the point A Where the conjugate surfaces leave one another. This is a point of low pressure at which it would be expected that light volatile materials would separate from a mixture.

The operation of the apparatus will now be readily understood in view of the above description. As an example, the operation will be more particularly related to the pumping of wood pulp in the paper industry. The material lto be pumped is a mixture of comminuted wood 0r wood pulp mixed with water arriving from a chute. A considerable amount of air is `mixed with the water and pulp and this more or less homogeneous mixture enters the pump through the inlet opening 14. The screws 16 and 28 seize the material and cause it to iiow in the well-known manner from the inlet opening 14 to the outlet opening 15. It does so at consilerable ow rate and raises the pressure of the material to a higher value so that it may be caused to ow through a conduit system. In the process of being pumped, however, the air due to the pumping action separates from the solid and liquid portions of the mixture and forms a pocket which affects the volumetric eiiiciency of the pump. In FIG. 4, the prior art type of pump working with such material gave a flow rate indicated by the lower straight line in 3 which it can be noted that -the volumetric eiciency was low.

By use of the present invention, however, the air lmay be removed from the pump housing through the openings 23 and 32 which are located at an optimum place for receiving such air. The air ows from the openings through the conduits and valves back to the inlet opening 14 0f the pump. The air is released into the atmosphere but, during the owinga certain amount of the solid and liquid is entrapped with the air and is released into the inlet area for circulation through the pump. In a practical application of the present invention, the pump was used to pump wood pulp mixed with water and air through a long conduit passing over buildings and mounted on brackets. The presence of the air in the wood pulp and liquid made the otherwise incompressible material act as though it had springs in it which set up a vibrating system which presented considerable shock to the building which supported the pipe. By use of the present invention, the air was removed from the wood pulp and the vibrations stopped.

It can be seen that a high slip component of the partially-separated heterogeneous mixture may be substantially removed from the pressurizing area of the pump. By removing the high slip material at that point, a minimum of pump slip occurs with that fluid and little occurs any way with the heavier fluid. The pump slip from the pressurizing area to the intake area through the operating clearances directly displaces that volume of intake to the pumping chamber; in the case of a compressible uid, this'would be an expanding volume. Therefore, clearances and corresponding slip rates become very important when handling heterogeneous materials. It becomes necessary to use additional means to maintain volumetric eiciency. The curve which is obtained is the upper curve inFIG. 4 and, as can be seen, a substantially greater volumetric efficiency is obtained. By use of the present invention, rotary pump volumetric eiciency can be increased, and air binding prevented, when handling partially separated heterogeneous mixtures of solids and/or fluids, by removing the high slip huid from the pressurizing area. Undesirable excess light iluid can be removed from the system handling the mixture through a rotary pump; for instance, air may be removed from paper stock, water or light liquids may be removed from some slurries, and

light iluids may be removed from viscous-light emulsions. The efliuent volume can be closely controlled by the use of the valves and the eflluent can be directed for elimination or return to the uid system. In addition, the etiluent may be observed visually and monitored by passing it through a cle'ar tubing at the low pressure.

It is obvious that minor changes may be -made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, desired to conline the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent is:

1. A pump of the double screw type comprising:

(a) a housing having spaced apart inlet and outlet openings at opposite ends of an intermediate portion having two intersecting cylindrical bores of the same diameter extending horizontally at the same level to maintain communication between the inlet and outlet openings.

(b) a pair of rotors with conjugated intermeshing helical surfaces rotatably positioned in the housing for rotation in opposite directions with their intermeshing portions moving upwardly to propel the material from the inlet to the outlet opening, and

(c) a conduit extending upwardly from the upper por tion of each bore about midway of its length and opening into the inlet opening for the release of gaseous uids.

2. The pump of claim 1, in which the periphery of each rotor remains during its rotation in engagement with its respective cylindrical bore during the entire portion of its revolution during which it is intermeshed with the other rotor.

3. The pump of claim 1, in which each conduit includes a valve for controlling the ow of fluids therethrough.

References Cited UNITED STATES PATENTS 2,381,695 8/ 1945 Sennet 103--128 2,623,469 12/1952 Gray 103-128 2,908,226 10/ 1959 Rich et a1. 103-128 ANDRES H. NIELSEN, Primary Examiner. 

